In one type of tamper indicating closure, it is conventional to mold circumferentially spaced bridges in order to define a tamper indicating band on the closure. Such construction requires costly more complex molds which also require maintenance. Typical patents showing such tamper indicating closures comprise U.S. Pat. Nos. 4,613,052, 4,721,218, 4,801,031, 5,090,246 and 5,090,788.
Another type of tamper indicating closure comprises utilizing an interrupted edged knife to produce bridges such as shown in U.S. Pat. No. 4,322,009.
In another type of tamper indicating closure, circumferentially spaced axial bridges are provided on the internal surface of the skirt of the closure and a continuous edged knife is applied from the exterior surface cutting through the wall of the closure and into the bridges. Such a construction also requires costly complex molds that require maintenance and necessitates relatively thin walls on the closures. A typical patent showing such a construction comprises U.S. Pat. No. 4,545,496.
Among the objectives of the present invention are to provide a tamper indicating closure on a molded plastic closure which does not require molded bridges; which can be made by relatively simple less costly molds; wherein the precise configuration of the bridges can be adjusted as desired; and wherein the bridges can be made at relatively high speeds and the desired configuration and strength of the bridges can be maintained; and wherein an improved method and apparatus insure accurately dimensional bridges.
In accordance with the invention, a tamper indicating closure comprises a base wall and a peripheral skirt having an internal thread adapted to engage the threads of a container wherein a tamper indicating band is provided on the skirt by a plurality of circumferentially spaced bridges. The band includes portions adapted to engage an annular bead on the container. The bridges are formed by using a primary knife having an interrupted cutting edge to produce a circumferential score in the side wall of the closure leaving spaced connectors or bridges followed by using a secondary knife having a continuous cutting edge to provide a continuous external score line and an accurately dimensional radial thickness of the bridges. In a preferred method and apparatus, the closures engage the successive primary and secondary knives and are moved such that the closures roll relative to the knives.